Example of Scientific method: Flemming’s discovery of Penicillin

In the last post we discussed the steps involved in a scientific method. In this post we will discuss the same thing with an example. As I
mentioned, keen observation of surroundings is the key quality of a scientist.
Here I am citing an example that tells us the value of an unexpected
observation.

Penicillin discovery

Infant jaundice is a condition very
common in infants that is characterized by yellowish skin
colouration. The reason for infant jaundice is the presence of high levels of
bilirubin in the blood. This can lead to brain damage and death. Bilirubin is a
degradation product of hemoglobin and that is degraded and excreted
by liver. In infants, immature liver cannot convert this bilirubin and thus
bilirubin accumulates leading to infant jaundice. Now our point, how infant
jaundice is treated? A nurse in England(Rochford
Hospital in Essex) found out that exposure of infants intermittently to mild sun rays
can significantly reduce their yellowish skin colour. Later scientists
experimented on this simple observation and found out that UV rays in the
sunlight could degrade bilirubin into non-toxic products and can be readily
excreted in infants. Till now, for infant jaundice the same treatment is given
all over the world. All started from a simple observation ultimately became a
treatment modality followed all over the world for a fatal disease.

Scientific method at work

Here we will discuss the steps involved in
the discovery of antibiotic penicillin byAlexander
Flemming(1928) During Second
World War, penicillin was widely used and could save millions from wound
infections.

Discovery of penicillin was serendipity or
an accidental discovery. Flemming was working on different aspects of growth of
bacterium namelyStaphylococcusthat cause throat infection. He plated
bacterial colonies on a medium in petri-plates for an experiment. Next day, he
found out that his bacterial cultures were ruined by a blue green fungus,Penicillium notatumcolonies. Instead of throwing away the
plates, he made an important observation that bacterial colonies could not grow
around this fungal colonies. He wants to know the reason. He asked why?

Now let us check out

How Flemming solved his problem using scientific
method?

Step I: observation and defining the problem.

Flemming’s observation was bacterial colonies could not grow around
fungal colonies.

Experimental Design:Two culture tubes A and B with nutrient broth for bacterial growth.

To the first tube, let it be A (“test” tube), he added fungus and
allowed to grow for few days.

He kept second tube, tube B as control (remained sterile)

After few days, he filtered the broth to remove any fungal cells and
allowed bacteria to grow in both tubes A and B.

Step IV: Collect and record data.

In the A tube (test), no bacterial growth were observed.

In the B tube (control), bacterial growth was observed.

Step V: Analyse and interpret data and draw conclusions.

He concluded that in tube A, previously grown fungal cells secreted
certain chemicals that inhibited the growth of bacteria. In tube B, bacteria
could grow as no fungal colonies were grown before. Thus hypothesis put forward
was correct.

Step VI: Report results or theorising:

Later he could isolate antibiotic penicillin fromPenicillium notatumcolonies.This discovery was during Second
World War. Penicillin was called “wonder drug” as millions of lives were saved
from bacterial wound infection due to the discovery of this antibiotic. Let us
summarise these accidental unexpected discoveries as said by famous
microbiologistLouis Pasteur“Luck favours the prepared mind”.